Transcript for Looking For Large Pieces of Debris From Flight 370 as Time Runs Out

This evening, as investigators try to close in on what could be debris, they're up against the clock. About 16 days left before the black boxes go silent, making the search even harder. I want to bring in ABC's aviation expert, retired colonel Steve ganyard. You have reminded us every step of the way about the race against time. Without the boxes pinging, this could be very difficult to find at the bottom of the Indian ocean. That's right, David. The black boxes are going to be the key. We'll never know what we need to know until we get to them. It's so deep in that part of the world. Up to 12 empire state buildings deep. You have currents. You have winds. You have all these things, the elements working against the rescuers. But the real race is against time at this point. Steve, you talk about the currents. The satellite photos we've been studying today, they were taken four days ago. If that was, in fact, debris, how far could it have traveled by now? The currents will affect the debris. And the winds will affect the debris. In that part of the world, the winds are howling and the currents are very strong. So, maybe, three, four, five miles per hour. Multiply that by 24 hours in a day. And the debris field gets pushed along every day. But more importantly, it gets spread out. And that makes it harder to find out where the rough wreckage is on the bottom of the ocean. Steve ganyard with us again tonight. Our thanks to Steve.

This transcript has been automatically generated and may not be 100% accurate.

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